Monday, December 14, 2009

Live on TV: An Implantable Cardiac Defibrillator Fires

As implantable cardiac defibrillators (ICDs) are increasingly ubiquitous in society, it is not suprizing that their effects might be caught on television. We've already seen the remarkable benefit of an ICD correcting ventricular fibrillation in the professional Belgian soccer player, Anthony Van Loo, but when it happens to a conscious scientist at the 2009 Coppenhagen Climate Summit, it certainly turns heads:

Danish physicist Henrik Svensmark was attending the Coppenhagen Climate Summit '09 and had three repetitive ICD firings recorded on live television. Reportedly he was rushed to a hospital and his condition stabilized.

Implantable cardiac defibrillators fire when the ventricular heart rates exceed a pre-determined heart rate that is sustained for a predetermined number of heart beats. It is unclear if his heart rate was elevated from a lower heart chamber (ventricular) arrhythmia (the most likely cause) or a racing upper chamber (atrial) heart rhythm abnormality that drove the lower chamber too fast. Unlike Mr. Van Loo, Dr. Svensmark heart rate was probably not fast enough to cause him to lose consciousness. Nonetheless, when the defibrillator fires, it delivers the equivalent of approximately 830 volts in a tenth of a second, causing the muscles of the chest, heart, vocal coards and diaphragm to contract forcefully, occassionally resulting in the "yelp" heard at the just before the video ends.

Communicating with the patient's ICD with a programmer after such an event helps doctors determine the cause of ICD firings and assure the device was working as expected. Based on that information, medication therapies or device adjustments can be made to help prevent future firings.

It should be noted that this event was NOT a "heart attack," or a sudden disturbance of the blood flow that supplies the heart, but rather an implantable cardiac defibrillator treating the sudden onset of a potentially lethal heart rhythm disturbance. As such, because the defibrillator responds so quickly, heart muscle function is usually preserved.

Yikes, an inappropriate shock! Don't you think the device companies should be doing more to increase detection specificity? The number of inappropriate shocks is alarming and companies are slow to improve their algorithms due to FDA scrutiny. The EP community ought to be outraged!

Thanks to Dr. Wes and my ICD I'm alive and only two shocks in six years - both very much appropriate. ICD, never leave home without it. And it's a heck of lot better than the 300 joule external cardiovert delivered courtesy of the paramedics while I was still conscious.

Hey Dr. Fisher,My boss forwarded this link to our team to take a look at the video. I was surprised to see it's your blog. I had to tell everyone that I used to work with you and what a great EP you are. Pretty interesting stuff you're posting here.

About Me

Westby G. Fisher, MD, FACC is a board certified internist, cardiologist, and cardiac electrophysiologist (doctor specializing in heart rhythm disorders) practicing at NorthShore University HealthSystem in Evanston, IL, USA and is a Clinical Associate Professor of Medicine at University of Chicago's Pritzker School of Medicine. He entered the blog-o-sphere in November, 2005.
DISCLAIMER: The opinions expressed in this blog are strictly the those of the author(s) and should not be construed as the opinion(s) or policy(ies) of NorthShore University HealthSystem, nor recommendations for your care or anyone else's. Please seek professional guidance instead.